Re: [libvirt] [PATCH] libxl: open libxl log stream with libvirtd log_level

On Wed, Nov 11, 2015 at 04:57:59PM +0100, Marek Marczykowski-Górecki wrote: > On Tue, Sep 15, 2015 at 11:21:00AM -0600, Jim Fehlig wrote: > > Daniel P. Berrange wrote: > > > On Tue, Sep 15, 2015 at 10:57:50AM -0600, Jim Fehlig wrote: > > > > > >> Daniel P. Berrange wrote: > > >> > > >>> On Tue, Sep 15, 2015 at 09:26:23AM -0600, Jim Fehlig wrote: > > >>> > > >>> > > >>>> Instead of a hardcoded DEBUG log level, use the overall > > >>>> daemon log level specified in libvirtd.conf when opening > > >>>> a log stream with libxl. libxl is very verbose when DEBUG > > >>>> log level is set, resulting in huge log files that can > > >>>> potentially fill a disk. Control of libxl verbosity should > > >>>> be placed in the administrator's hands. > > >>>> > > >>>> Signed-off-by: Jim Fehlig <jfehlig(a)suse.com&gt; > > >>>> --- > > >>>> src/libxl/libxl_conf.c | 18 +++++++++++++++++- > > >>>> 1 file changed, 17 insertions(+), 1 deletion(-) > > >>>> > > >>>> > > >>> ACK, this makes sense as default behaviour. As a future enhancement > > >>> you might also consider supporting a config setting in /etc/libvirt/libxl.conf > > >>> to explicitly control the libxl library logging behaviour independantly. > > >>> > > >>> > > >> I had actually thought of adding it there first, but then took this > > >> approach assuming it would be more receptive upstream :-). Personally, > > >> I'm on the fence. I like the idea of a single knob to control log level > > >> throughout the daemon, making it a bit easier on admins. On the other > > >> hand, individual knobs are more friendly to those pouring through logs. > > >> I can add a knob in libxl.conf if preferred. > > >> > > > > > > After thinking about it some more, I could actually see value in > > > create a dedicated virLogSource() instance, solely for libxl > > > library messages. If we then created a virLogSourceGetPriority() > > > method, you could query that to see if to turn on logging for > > > the libxl library. That would ultimately allow you to turn on > > > debug for just the libxl library if desired, eg > > > > > > static virLogSource virLogLibXL = { > > > .name = "libxl.libxl_library", > > > .... > > > } > > > > > > LIBVIRT_LOG_FILTERS="1:libxl_library" > > > > > > > Ah, good idea. I'll look into it. > > Is it done anywhere? If not, how can I help? > > This the above change (setting libxl log level to libvirtd global one), > makes almost impossible to get libxl debug, because the rest of libvirtd > trashes the logs (hundreds virEvent* and virObject* messages, at > "info"(!) level). Presumably that's because you are using LIBVIRT_DEBUG=1 or setting log_debug=1 in /etc/libvirt/libvirtd.log. That is generally discouraged because it turns on all logging, which is essentially unusably verbose. It is also better to use more specific log settings, eg when I debug the QEMU driver I usually use log_filters="1:qemu 1:security 3:event 3:object 1:util" log_outputs="1:file:/var/log/libvirt/libvirtd.log" This generates log messages from every source file in qemu and security directories, and also log messages from every file in the util/ directory *except* for event & object files. So it is much more managable to read.

The log filter strings just do a wildcard match against the VIR_LOG_INIT("...."); lines in each source file, so you can make things more or less specific as you desire. Regards, Daniel